[Mesa-maintainers] Downstream Mesa patches and quirks

[Michal Srb]

On úterý 20. února 2018 12:47:27 CET Stefan Dirsch wrote:
> - n_Disable-AMDGPU-GFX9-Vega-on-LLVM-lessthan-6.0.0.patch
>   * Disable AMDGPU GFX9/Vega with LLVM < 6.0.0.
>     While it is supported since LLVM 5.0.0, it was not working
>     correctly (bnc#1075901). Since we do not have the resources to
>     determine which fixes should be backported and LLVM 6 will be
>     released relatively soon, disable the support until then. Users
>     with the card will have working desktop using software
>     rendering just like they did with LLVM 4.
>  https://build.opensuse.org/package/view_file/X11:XOrg/Mesa/n_Disable-AMDGPU
> -GFX9-Vega-on-LLVM-lessthan-6.0.0.patch?expand=1
> https://bugzilla.suse.com/show_bug.cgi?id=1075901
> 
>  Not sure, whether this change would be appreciated upstream in git. Michal?

My guess is that it would not be. There is no bug in Mesa, the bug is in LLVM. 
LLVM 5 is supposed to support Vega, but it has a bug that breaks it. LLVM 6 
works. The correct thing to do would be to find and backport the fix into LLVM 
5, but we can not do it since we do not have the (very new) hardware. So we 
decided to disable Vega support in Mesa if built with LLVM 5.

If there was a configuration option to disable parts of AMDGPU, we would use 
it. But there is not, hence this patch.

Michal